The present invention relates in general to a control circuit for testing equipment which is simple in construction, reliable in service and inexpensive to manufacture compared to devices currently available for performing similar functions. The circuit can be used in a device for detecting and counting broken filaments in a strand, for example. It may also be used, in a modified version, as a self compensating measuring circuit for use in a tachometer or any other similar device used to measure rotational or linear speeds, by measuring the presence or absence of light using apertured discs and/or strips.
In systems used heretofore to measure or detect random faults or to measure rotational or linear speeds utilizing light sources, the measuring devices typically have used two circuits, one circuit to sense the light and one circuit to control the emission of the light. Thus, one circuit used to control the light emission required a control loop that was optically complicated since it required beam splitters, detectors and feedback amplifiers to provide a constant light flux. The other circuit of the prior art devices, where the light beam receiver was employed was subject to drifts due to temperature and therefore required automatic control circuits for temperature control and compensators within the circuit to eliminate such drifts.
In accordance with the instant invention, a system is provided which eliminates the need for such complicated circuitry rendering Applicant's system simple in construction, very reliable in service, and as heretofore stated, inexpensive from a manufacturing standpoint so that it can readily be used in devices such as tachometers and optical devices utilized to detect broken filaments in textile strands, to name but two applications.